if you have another computer or another hard drive laying around, put your wierd hard drive into that computer or put the spare hard drvie in your computer.

Boot to windows on the different hard drive, the one without the problem. Then see if you can see all of your partitions in "my computer", they will appear as seperate drives. If you only see 2 new drives instead of three that means that a partition is no longer partitioned and you have lost your data.

Or boot to the XP cd and check all of your partitions. If you see unpartitioned space that is more than 8mbs then a partition was deleted,